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Birth Control Pill

Your doctor can prescribe birth control pills to prevent pregnancy. When taken properly, birth control pills are 99 per cent effective. The pill doesn't protect you against sexually transmitted infections.

Birth control pills contain low doses of both estrogen and progestin. One type contains progestin alone. These hormones are similar to the natural hormones that control a woman's menstrual cycle. Different brands of pills contain different amounts of estrogen and progestin. Changing the brand of pill can prevent side effects in some cases. When a woman takes birth control pills:

her ovaries stop releasing eggs

the mucus in her cervix gets thick making it harder for sperm to enter

the lining of the uterus gets thinner making it hard for a fertilized egg to attach to the wall

How to Use Birth Control Pills

There are many types of birth control pills. Most brands come as 21-day or 28-day packs. A 28-day pack contains 21 birth control pills and seven sugar pills, and a new 28-day pack is started as soon as the old one is finished. A 21-day pack contains 21 birth control pills. After taking these 21 pills, wait seven days before starting a new 21-day pack. Read the instructions in the package and follow them carefully. For birth control pills to be most effective, you should take your pill at the same time each day.

Some things may stop the pill from working properly. The pill may not work as well:

during the first cycle when you are taking birth control pills for the first time

during the first cycle when you are taking birth control pills again after being off them